TABLE 16 Malnutrition in Preschool Children Grouped by Number of Preschool Children in Their Families, Candelaria, Colombia, 1963 Number of Preschool Total Malnourished Children Children/Family Population Number Percent 1 173 59 34.2 2 364 146 40.1 3 366 147 40.2 4 140 66 47.1 5 or more 25 13 52.0 Source: Wray and Aguirre (10). TABLE 17 Malnutrition in Preschool Children by Interval until Next Sibling, Bang Pa-In, Thailand, 1969 Interval between Child and Next Sibling (Months) Total Population Malnourished Children Number Percent Less than 24 More than 24 No child following 43 49 119 30 26 38 70 53 37 Source: A Health and Demographic Survey of Bang Pa-In (15). Douglas, in an investigation of factors associated with prematurity, also examined the effect of birth interval (67). His data were derived from interviews of all mothers who delivered babies during 1 week in March, 1946.* A large number of mothersó90.5 percent, or 13,687ócooperated in the interviews. Douglas found that social class differences in the risk of prematurity were present but relatively unimportant. Risks appeared to be greatest in "two well-defined groups of working-class women, namely primiparae aged 20 or less, and multiparae with closely spaced pregnancies" (67, p. 159). After examining his data further, Douglas made the following comment: ... In the present survey 48 percent of working-class mothers spaced their pregnancies either so closely or so far apart that they ran an abnormally high risk of giving birth to a premature baby. If they all could have *It was from these children that the sample of 5,386 were selected for follow-up in the National Survey of Health and Development in the United Kingdom, referred to earlier (33, 34, 35).ndex child and following sibling) and malnutrition and found a similar, statistically significant effect, as indicated in Table 17.